Aircraft Tire Manual

AIRCRAFT TIRE CARE AND MAINTENANCE

REVISED - 10/04

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Contents Page

Section INTRODUCTION 31 GENERAL DATA

Bias Aircraft Tire Construction 4Radial Aircraft Tire Construction 6Tire Terminology 8Tire Marking 9Aircraft Tire Serial Number Codes 10

2 PREVENTIVE MAINTENANCEProper Inflation Procedures 11

Cold Pressure Setting 12Procedures for Hot Tire Inflation Pressure Checks 12Special Procedures – Emergency Tire Stretch 13

Other Preventive Maintenance 13Casing Flat Spotting 13Cold Weather Precautionary Hints 13Special Procedures – Above Normal Braking Energy 14Protecting Tires from Chemicals and Exposure 14Condition of Airport and Hangar Floor Surfaces 14

3 MOUNTING & DEMOUNTINGBefore Mounting 15

Bias and Radial Aircraft Tire Guidelines 15Aircraft Wheels 15Aircraft Tire Conductivity 16Matching Dual Tires 16

Mounting Procedures 16Tube-Type 17Tubeless Tires 17Tubes in Tubeless Tires 18

Inflation Pressure Loss in Tubeless Assemblies 18Tire Balancing and Landing Gear Vibration 20Aircraft Tire/Wheel Balancer for General Aviation Operation 20Demounting 21

4 INSPECTION, STORAGE & SHIPPINGInspecting Mounted Tires 22

Typical Treadwear Patterns 23Tread Conditions 24Sidewall Conditions 27Bead Conditions 28Casing Conditions 28

Tire and Tube Storage 29Tire and Tube Age Limit 29

Storage of Mounted Assemblies 30Shipping 30

Shipping Inflation 30Shipping and Handling Damage 30

5 RETREADINGRetreading Tires 31

6 AIRCRAFT TIRE PROPERTIESTire Name Size Classification 32Aircraft Tire -vs- Other Tire Applications 33

7 EFFECTS OF OPERATING CONDITIONS Centrifugal Force 34

Traction Wave 35Groove Cracking 37Rib Undercutting 37

Heat Generation 38Tensile, Compression and Shear Forces 43Tire Inflation 48Limited Warranty 49Notes 50Tire Performance Envelope Diagram 51

Notice: This Aircraft Tire Care and Maintenance Manual effective 10/04 combines information from previousGoodyear Aircraft Tire Care and Maintenance manuals and supercedes all previous manuals.

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Introduction

The information in this manual is designed to help aircraft owners and maintenance personnel obtain maximum service life from their bias and radial aircraft tires. The discussions contained in this part aredesigned not only to teach how to properly operate and maintain aircraft tires, but also to demonstrate whythese techniques and procedures are necessary.

Aircraft operating conditions require a wide variety of tire sizes and constructions. The modern aircraft tireis a highly-engineered composite structure designed to carry heavy loads at high speeds in the smallest andlightest configuration practical. Despite this, tires are one of the most underrated and least understoodcomponents on the aircraft. The general consensus is that they are “round, black, and dirty,” but in reality,they are a multi-component item consisting of three major materials: steel, rubber and fabric. By weight, anaircraft tire is approximately 50% rubber, 45% fabric, and 5% steel. Taking this one step further, there aredifferent types of nylon and rubber compounds in a tire construction, each with its own special properties designed to successfully complete the task assigned.

Goodyear aircraft tire technology includes Computer Aided Design along with Finite Element Analysis, aswell as the science of compounds and materials applications. Materials and finished tires are subjected to avariety of laboratory, dynamometer, and field evaluations to confirm performance objectives and obtaincertification.

The manufacturing process requires the precision assembly of tight-tolerance components and a curingprocess under carefully controlled time, temperature and pressure conditions. Quality assurance proceduresensure that individual components and finished tires meet specifications.

The Goodyear Technical Center and all Goodyear Aviation Tire new and retread tire plants are ISO 9001:2000 certified.

NOTE: The procedures and standards included in this manual are intended to supplement the specificinstructions issued by aircraft and wheel/rim manufacturers.

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BIAS PLY AIRCRAFT TIRE CONSTRUCTIONBias aircraft tires feature a casing which is constructed of alternate layers of rubber coated ply cords which extend around the beads and are at alternate angles substantially less than 90° to the center line of the tread.

1General Data

TREAD

GROOVES BUFF LINE CUSHION

BREAKERS/BELTS

TREAD REINFORCING PLY

INNERLINER

BEAD HEEL

BEAD TOE

APEX STRIP

SIDEWALL

CASING PLIES

CHAFERS

PLY TURNUPS

FLIPPERS

CHINE CHINE

WIRE BEADS

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General Data 1BIAS PLY AIRCRAFT TIRE CONSTRUCTION (CONT’D)

Glossary

Apex Strip The apex strip is a wedge of rubber affixed to the top of the bead bundle.

Bead Heel The bead heel is the outer bead edge that fits against the wheel flange.

Bead Toe The bead toe is the inner bead edge closest to the tire centerline.

Breakers Breakers are reinforcing plies of rubber coated fabric placed under the buffline cushion to protect casing plies and strengthen and stabilize tread area. They are considered an integralpart of the casing construction.

Buff Line The buff line cushion is made of rubber compound to enhance the adhesion between Cushion the tread reinforcing ply and the breakers or casing plies. This rubber layer is of sufficient

thickness to allow for the removal of the old tread when the tire is retreaded.

Casing Plies Plies are alternate layers of rubber-coated fabric (running at opposite angles to one another)which provide the strength of the tire.

Chafer A chafer is a protective layer of rubber and/or fabric located between the casing plies andwheel to minimize chafing.

Chines Also called deflectors, chines are circumferential protrusions that are molded into the sidewall of some nose tires that deflect water sideways to help reduce excess water ingestioninto the engines.

Flippers These layers of rubberized fabric help anchor the bead wires to the casing and improve thedurability of the tire.

Grooves Circumferential recesses between the tread ribs.

Liner In tubeless tires, this inner layer of low permeability rubber acts as a built-in tube andrestricts gas from diffusing into the casing plies. For tube-type tires a thinner rubber liner isused to prevent tube chafing against the inside ply.

Ply Casing plies are anchored by wrapping them around the wire beads, thus forming the ply Turnups turnups.

Sidewall The sidewall is a protective layer of flexible, weather-resistant rubber covering the outercasing ply, extending from tread edge to bead area.

Tread The tread is made of rubber, compounded for toughness, durability and wear resistance. The tread pattern is designed in accordance with aircraft operational requirements. The circumferential ribbed tread is widely used today to provide good traction under varying runway conditions.

Tread Tread reinforcement is one or more layers of fabric that strengthen and stabilize the treadReinforcing area for high-speed operation. It also serves as a reference for the buffing process in

Ply retreadable tires.

Wire Beads The beads are hoops of high tensile strength steel wire which anchor the casing plies andprovide a firm mounting surface on the wheel.

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1General Data

RADIAL PLY AIRCRAFT TIRE CONSTRUCTIONRadial aircraft tires feature a flexible casing which is constructed of rubber coated ply cords which extendaround the beads and are substantially at 90° to the centerline of the tread. The casing is stabilized by anessentially inextensible circumferential belt.

CHINE CHINE

BEAD HEEL

LINER

BEADS

BEAD TOE

APEX STRIP

BUFF LINE CUSHIONOVERLAY

BELT PLIES

CASINGPLIES

CHIPPERS

PLY TURNUPS

SIDEWALL

TREAD

GROOVES

TREAD REINFORCING PLY

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General Data 1RADIAL PLY AIRCRAFT TIRE CONSTRUCTION (CONT’D)

Glossary

Apex Strip The apex strip is a wedge of rubber affixed to the top of the bead bundle.

Bead Heel The bead heel is the outer bead edge that fits against the wheel flange.

Bead Toe The bead toe is the inner bead edge closest to the tire center line.

Belt Plies This is a composite structure which stiffens the tread area for increased landings. The beltplies increase the tire strength in the tread area.

Buff Line The buff line cushion is made of rubber compounded to enhance the adhesion between the Cushion tread reinforcing ply and the overlay. This rubber layer is of sufficient thickness to allow for

the removal of the old tread when the tire is retreaded.

Casing Plies Casing plies are layers of rubber-coated fabric which run radially from bead to bead. The casing plies provide the strength of the tire.

Chippers The chippers are layers of rubber coated fabric applied at a diagonal angle which improvethe durability of the tire in the bead area.

Chines Also called deflectors, chines are circumferential protrusions that are molded into the sidewall of some nose tires that deflect water sideways to help reduce excess water ingestioninto the engines.

Grooves Circumferential recesses between the tread ribs.

Liner In tubeless tires, this inner layer of low permeability rubber acts as a built-in tube andrestricts gas from diffusing into the casing plies. For tube-type tires, a thinner rubber liner isused to prevent tube chafing against the inside ply.

Overlay The overlay is a layer of reinforcing rubber coated fabric placed on top of the belts to aid inhigh speed operation.

Ply Turnups Casing plies are anchored by wrapping them around the wire beads, thus forming the plyturnups.

Sidewall The sidewall is a protective layer of flexible, weather-resistant rubber covering the outer casing ply, extending from tread edge to bead area.

Tread The tread is made of rubber, compounded for toughness, durability, and tread wear. Thetread pattern is designed in accordance with aircraft operational requirements. The circumferential ribbed tread is widely used today to provide good traction under varying runway conditions.

Tread Tread reinforcement is one or more layers of rubber coated fabric that strengthen and Reinforcing stabilize the tread area for high-speed operation. This also serves as a reference for the

Ply buffing process in retreadable tires.

Wire Beads The beads are hoops of high tensile strength steel wire which anchor the casing plies andprovide a firm mounting surface on the wheel.

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1General Data

TIRE TERMINOLOGYPLY RATING - The term “ply rating” is used to indicate an index to the load rating of the tire. Years agowhen tires were made from cotton cords, “ply rating” did indicate the actual number of plies in the carcass.With the development of higher-strength fibers such as nylon, fewer plies are needed to give an equivalentstrength. Therefore the definition of the term “ply rating” (actual number of cotton plies) has been replacedto mean an index of carcass strength or a load carrying capacity.

RATED LOAD - This is the maximum allowable load that the tire can carry at a rated inflation pressure.

RATED PRESSURE - Rated pressure is the maximum inflation pressure to match the load rating. Aircrafttire pressures are given for an unloaded tire; i.e, a tire not on an airplane. When the rated load is applied tothe tire, the pressure increases by 4% as a result of a reduction in air volume.

OUTSIDE DIAMETER - This measurement is taken at the circumferential center line of an inflated tire.

SECTION WIDTH - This measurement is taken at the maximum cross sectional width of an inflated tire.

RIM DIAMETER - This is the nominal diameter of wheel/rim on which the tire is mounted.

SECTION HEIGHT - This measurement can be calculated by using the following formula:

Section Height = Outside Diameter - Rim Diameter2

ASPECT RATIO - Measure of the tire’s cross section shape. This can be calculated by the following formula:

Aspect ratio = Section Height Section Width

FLANGE HEIGHT - This is the height of the wheel rim flange.

FLANGE DIAMETER - The diameter of the wheel including the flange.

FREE HEIGHT - This measurement can be calculated by using the following formula:

Free Height = Outside Diameter - Flange Diameter2

STATIC LOADED RADIUS - This is the measurement from the center of the axle to the runway fora loaded tire.

LOADED FREE HEIGHT - This measurement can be calculated by using the following formula:Loaded Free Height = Static Loaded Radius - Flange Diameter

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TIRE DEFLECTION - A common term used when talking about aircraft tires is the amount of deflection itsees when rolling under load. The term % Deflection is a calculation made using the following formula:

% Deflection = Free Height - Loaded Free HeightFree Height

Aircraft tires are designed to operate at 32% deflection, with some at 35%. As a comparison, cars and trucksoperate in the 17% range.

SERVICE LOAD (OPERATIONAL LOAD) – Load on the tire at max aircraft takeoff weight.

SERVICE PRESSURE (OPERATIONAL PRESSURE) – Corresponding pressure to provide proper deflectionat service load.

RATED SPEED – Maximum speed to which the tire is qualified.

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All Goodyear commercial aircraft tires are clearly marked with the following information: Goodyear, size,load rating, speed rating, molded skid depth, Goodyear part number, serial number, Goodyear plant identification and TSO marking. In addition, Goodyear tires are marked with the ply rating and other markings as required by airframe manufacturers or other organizations, such as an AEA code (which definesnew tire casing and tread construction).

All TSO-C62b qualified tires with a speed rating of 160 mph or less and all TSO-C62c qualified tires do notrequire requalification to TSO-C62d unless the tire is changed.

Tires retreaded by all of Goodyear’s facilities have the following information marked in the shoulder: the size, ply rating, speed category, retread plant and/or country of retreading, as well as retread level (R-Level), date of retreading and retread AEA code if appropriate.

COUNTRY OFMANUFACTURE

APPLICABLE SPEC REFERENCE

PLY RATING/SPEEDRATING/LOAD RATING

TUBELESS OR TUBETYPE

MOLD CODE

MOLDEDSKID

DEPTH

TIRE SIZE

TIRE NAME

SERIALNUMBER

PARTNUMBER

AEACARCASS/

TREADCODE

MANUFACTURER





MOLD CODE

MOLDEDSKID

DEPTH

TIRE SIZE

TIRE NAME

SERIALNUMBER

PARTNUMBER

AEACARCASS/

TREADCODE

MANUFACTURER





MOLD CODE

MOLDEDSKID

DEPTH

TIRE SIZE

TIRE NAME

SERIALNUMBER

PARTNUMBER

AEACARCASS/

TREADCODE

MANUFACTURER





MOLD CODE

MOLDEDSKID

DEPTH

TIRE SIZE

TIRE NAME

SERIALNUMBER

PARTNUMBER

AEACARCASS/

TREADCODE

MANUFACTURER

General Data 1TIRE MARKING

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AIRCRAFT TIRE SERIAL NUMBER CODESAll serials consist of eight (8) characters.

Example: YJJJNNNN

Position 1 (Y) represents the year of production

Positions 2, 3 and 4 (JJJ) signify day of year (Julian Date)

Note: Positions 1 through 4 fulfill requirements of MIL-PRF-5041J for military tires.

Positions 5, 6, 7 and 8 (NNNN) signify the Individual Tire ID Number

Danville’s tire IDs range from 0001 to 4999

Thailand’s production ranges from 5000 to 5999

Brazil’s production ranges from 7000 to 7999

For production prior to January 1, 2001, tires produced in Thailand showed a ‘T’ in the 5th position, and tiresproduced in Brazil had a ‘B’ in the 5th position. Tire IDs for both plants (positions 6, 7 and 8) were 001 through999. Danville tire IDs have always been 0001 through 4999.

1019 12342001 Danville

EXAMPLES

TIRE ID

2019 51232002 Thailand

JULIAN DAY TIRE ID

JULIAN DAY

3019 71232003 Brazil

JULIAN DAY TIRE ID

1General Data

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Tires cannot be taken for granted on any aircraft. Tire maintenance costs will be at their lowest and tire lifewill be at its longest if proper maintenance practices are observed. Safe tire operation also depends onproper maintenance. Thus, preventive tire maintenance leads to safer, more economic operations.

PROPER INFLATION PROCEDURESNOTE: Keeping aircraft tires at their correct inflation pressure is the most important factor in any

preventive maintenance program.

The problems caused by incorrect inflation can be severe. Overinflation can cause uneven treadwear, reducetraction, make the tread more susceptible to cutting and increase stress on aircraft wheels. Underinflationproduces uneven tire wear and greatly increases stress and flex heating in the tire, which shortens tire lifeand can lead to tire blowouts. More information about the effects of improper inflation is available in thesection “Effects of Operating Conditions.”

1. CHECK DAILY WHEN TIRES ARE COOLTire pressures should always be checked with the tire at ambient temperatures. Tire temperatures canrise in excess of 200˚F (93˚C) above ambient during operation. A temperature change of 5˚F (3˚C) produces approximately one percent (1%) pressure change. It can take up to 3 hours after a flight fortire temperatures to return to ambient.A tire/wheel assembly can lose as much as five percent (5%) of the inflation pressure in a 24-hour periodand still be considered normal. This means that tire pressures change on a daily basis. Even a tire whichdoes not normally lose pressure can become damaged by FOD or other outside factors that can suddenlyincrease pressure loss. These are all reasons why it is important to check pressure daily or before each flight.

2. INFLATE TO WORST CONDITIONSWhen tires are going to be subjected to ground temperature changes in excess of 50˚F (27˚C) because offlight to a different climate, inflation pressures should be adjusted to worst case prior to takeoff. Theminimum required inflation must be maintained for the cooler climate; pressure can be readjusted inthe warmer climate. Before returning to the cooler climate, adjust inflation pressure for the lower temperature. An ambient temperature change of 5˚F (3̊ C) produces approximately one percent (1%)pressure change.

3. USE DRY NITROGEN GAS (WHEN REQUIRED)Nitrogen will not sustain combustion and will reduce degradation of the liner material, casing plies andwheel due to oxidation.

4. INCREASE PRESSURE 4% FOR TIRES UNDER LOADIt must be determined if “loaded” or “unloaded” pressure has been specified by the aircraft manufacturer.When a tire is under load, the gas chamber volume is reduced due to tire deflection. Therefore, ifunloaded pressure has been specified, that number should be increased by four percent (4%) to obtainthe equivalent loaded inflation pressure. The opposite is true as well: if loaded pressure has been specified, that number should be reduced by four percent (4%) if the tire is being inflated while unloaded.

5. ALLOW 12-HOUR STRETCH AFTER MOUNTINGAll tires, particularly bias tires, will stretch (or grow) after initial mounting. This increased volume of thetire results in a pressure drop. Consequently, tires should not be placed in service until they have beeninflated a minimum of 12 hours, pressure rechecked, and tires re-inflated if necessary.

6. NEVER REDUCE PRESSURE ON A HOT TIREExcess inflation pressure should never be bled off from hot tires. All adjustments to inflation pressureshould be performed on tires cooled to ambient temperature. Procedures for hot tire inflation pressurechecks are described later in this session.

7. EQUAL PRESSURE FOR DUALSTo prevent one tire on a gear from carrying extra load, all tires on a single gear should be inflated equally.The mate tire(s) will share the load, allowing individual tires to run underinflated or overloaded if pressures are unequal, because all tires on the gear will deflect identically.

8. CALIBRATE INFLATION GAUGE REGULARLYUse an accurate, calibrated gauge. Inaccurate gauges are a major source of improper inflation pressures.Gauges should be checked periodically and recalibrated as necessary. Goodyear recommends the use ofa digital or dial gauge with 5 PSI increments and a memory needle.

PreventiveMaintenance 2

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PROPER INFLATION PROCEDURES (CONT’D)

Mounted Tube-Type TiresA tube-type tire that has been freshly mounted and installed should be closely monitored during the firstweek of operation, ideally before every takeoff. Air trapped between the tire and the tube at the time ofmounting will seep out under the beads, through sidewall vents or around the valve stem, resulting in an underinflated assembly.

Mounted Tubeless TiresA slight amount of gas diffusion through the liner material and casing of tubeless tires is normal. The sidewalls are purposely vented in the lower sidewall area to bleed off trapped gases, preventing separationor blisters. A tire/wheel assembly can lose as much as five percent (5%) of the inflation pressure in a 24-hour period and still be considered normal. If a soap solution is used to check leaks, it is normal forsmall amounts of bubbles to be observed coming from the vent holes.

COLD PRESSURE SETTINGThe following recommendations apply to cold inflation pressure setting:

1. Minimum service pressure for safe aircraft operation is the cold unloaded inflation pressure specified bythe airframe manufacturer.

2. The loaded service inflation must be specified four percent (4%) higher than the unloaded inflation.

3. A tolerance of minus zero (-0) to plus five percent (+5%) of the minimum pressure is the recommendedoperating range.

4. If “in-service” pressure is checked and found to be less than the minimum pressure, the following tableshould be consulted. An “in-service” tire is defined as a tire installed on an operating aircraft.

PROCEDURES FOR HOT TIRE INFLATION PRESSURE CHECKS

When it is deemed necessary to make “hot” tire inflation pressure checks between normal 24 hourly “cold” tire pressure checks, follow these procedures to identify any tire that has lost pressure faster than its axle mate(s).

Cold Tire Service Pressure Recommended Action

100 to 105 percent of loaded service pressure None - normal cold tire operating range.

95 to less than 100 percent of loaded service pressure Reinflate to specified service pressure.

90 to less than 95 percent of loaded service pressure Inspect tire/wheel assembly for cause of pressure loss.Reinflate & record in log book.Remove tire/wheel assembly if pressure loss is greater than 5% and reoccurs within 24 hours.

80 to less than 90 percent of loaded service pressure Remove tire/wheel assembly from aircraft (See NOTE below).

Less than 80 percent of loaded service pressure Remove tire/wheel assembly and adjacent tire/wheel assembly from aircraft (See NOTE below).

0 percent Scrap tire and mate if air loss occurred while rolling (See NOTE below).

NOTE: Any tire removed due to a pressure loss condition should be returned to an authorized repair facility or retreader, along with a description of the removal reason, to verify that the casing has not sustained internal degradation and is acceptable for continued service.

Do not approach a tire/wheel assembly that shows signs of physical damage which might compromise its structural integrity. If such conditions exist refer to operator safety procedures

for damaged tire/wheel assemblies.

THIS PROCEDURE DOES NOT REDUCE OR REPLACE THE NEED AND IMPORTANCE OF 24-HOURLY “COLD” TIRE PRESSURE CHECKS.

Preventive2Maintenance

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PROPER INFLATION PROCEDURES (CONT’D)

• This procedure identifies, for a given multi-tire landing gear, the tire/wheel assembly that has lost inflation pressure at the fastest rate on a given landing gear. This procedure does not apply to the normal inflation pressure drop which all tires experience, and proposes no action for this case.

• Tires at elevated temperatures will develop inflation pressures higher than the specified cold inflationpressures. Excess inflation pressure should never be released from “hot” tires.

• Inflation pressure should be checked on all tires of a given landing gear before taking action.

- If any tire is less than 90% of minimum loaded service pressure, remove the tire from service.

- Determine the average pressure of all tires on the gear. Any tire(s) that is/are less than 95% of the average, should be inflated up to the average.

SPECIAL PROCEDURES – EMERGENCY TIRE STRETCHIn an emergency situation, tires which must be placed in service without being inflated a minimum of 12hours should be inflated to 105% of the unloaded service pressure. The tire/wheel/valve assembly shouldbe sprayed with a soap solution and checked for abnormal leakage (abnormal leakage is if the soap solution bubbles anywhere on the wheel or if a constant stream of bubbles is produced at the tire vents). Ifthere is abnormal leakage, the tire/wheel assembly should be rebuilt according to normal procedures. Ifthere is no abnormal leakage, the tire can be placed in service, as long as cold tire pressure is checked beforeevery flight within the next 48 hours and the tire is re-inflated if necessary. Note: If the pressure dropsbelow 90% of service pressure during these checks, follow the guidelines per the Cold Tire Service Pressurechart in this section.

OTHER PREVENTIVE MAINTENANCECASING FLAT SPOTTINGLoaded tires that are left stationary for any length of time can develop temporary flat spots. The degree ofthis flat spotting depends upon the load, tire deflection and temperature. Flat spotting is more severe andmore difficult to work out during cold weather. Occasionally moving a stationary aircraft can lessen thiscondition. If possible, an aircraft parked for long periods (30 days or more) should be jacked up to removeweight from the tires. Under normal conditions, a flat spot will disappear by the end of the taxi run.

COLD WEATHER PRECAUTIONARY HINTSWhen extreme drops in temperature are experienced, these precautionary tips can help provide safe, trouble-free operation:1. Follow Goodyear’s recommendations on mounting as described on the new tire label.2. Use only new wheel manufacturer-approved O-ring seals with the proper cold weather properties,

properly lubricated and installed.3. Use only an accurate calibrated pressure gauge.4. Be sure that wheel bolts are properly torqued per wheel manufacturer’s instructions.5. Aircraft parked and exposed to cold soak for a period of time (1 hour or more), should have tire pressure

checked and adjusted accordingly.6. High speed taxis and sharp turns should be avoided to prevent excessive sideloading.7. An important fact to remember is that for every 5°F (3° C) change (increase) in temperature will result

in a corresponding one percent (1%) change (increase) in tire pressure.8. Do not reduce the inflation pressure of a cold tire that is subjected to frequent changes of ambient temperature.

PreventiveMaintenance 2

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OTHER PREVENTIVE MAINTENANCE (CONT’D)

SPECIAL PROCEDURES – ABOVE NORMAL BRAKING ENERGYTires that have been subjected to unusually high service braking or operating conditions such as HIGHENERGY REJECTED TAKEOFFS or HIGH ENERGY OVERSPEED LANDINGS* should be removed andscrapped. Even though visual inspection may show no apparent damage, tires may have sustained internalstructural damage. Consequently, affected tires inflated should be clearly marked and/or documented byserial number with a description of the reason for removal and returned to a full service tire supplier.

*Overspeed landings are those that exceed the tire speed rating.

Tires that have deflated due to a FUSE PLUG RELEASE should be removed and scrapped. If this hasoccurred in dynamic (rolling) conditions, the mate tires have been subjected to high stress conditions andshould also be removed. If this has occurred in a static (not rolling) condition, the mate tire does not haveto be removed unless it fails to pass other AMM or applicable Goodyear CMM service or inspection criteria.

For “HARD LANDINGS”, the AMM should be followed.

Also, all wheels should be checked in accordance with the applicable Wheel Overhaul or MaintenanceManual.

PROTECTING TIRES FROM CHEMICALS AND EXPOSURETires should be kept clean and free of contaminants such as oil, hydraulic fluids, grease, tar, and degreasingagents which have a deteriorating effect on rubber. Contaminants should be wiped off with denatured alcohol, then the tire should be washed immediately with soap and water. When aircraft are serviced, tiresshould be covered with a waterproof barrier.

Tire coatings or dressings: Goodyear adds antioxidants and antiozonants to the sidewall and tread to helpprevent premature aging from ozone and weather exposure. There are many products on the market that are advertised to clean tires and to improve appearance and shine. Since many of these may remove theantioxidants and antiozonants, we do not endorse any of them unless the tires are to be used for displaypurposes only.

Aircraft tires, like other rubber products, are affected to some degree by sunlight and extremes of weather.While weather-checking does not impair performance, it can be reduced by protective covers. These covers(ideally with light color or aluminized surface to reflect sunlight) should be placed over tires when an aircraft is tied down outside.

Store tires away from fluorescent lights, electric motors, battery chargers, electric welding equipment and electric generators, since they create ozone which has a deteriorating effect on rubber.

CONDITION OF AIRPORT AND HANGER FLOOR SURFACESRegardless of the excellence of any preventive maintenance program, or the care taken by the pilot andground crew in handling the aircraft, tire damage will certainly result if runways, taxi strips, ramps andother paved areas of an airfield are in a poor condition or improperly maintained. Foreign object damage(FOD) is the most common cause for early removals.

Chuck holes, cracks in pavement or asphalt, or stepoffs from pavement to ground can cause tire damage.Pavement breaks and debris should be reported to airport per-sonnel for immediate repair or removal.

Another hazardous condition is the accumulation of loosematerial on paved areas and hangar floors. These areas shouldbe kept clean of stones, tools, bolts, rivets and other foreignmaterials at all times. With care and caution in the hangars andaround the airport, tire damage can be minimized.Many majorairports throughout the world have modified their runway surfaces by cutting cross grooves in the touchdown and rolloutareas to improve water runoff. This type of runway surface cancause a pattern of chevron-shaped cuts in the center of the tread.As long as this condition does not cause chunking or cuts intothe fabric, the tire is suitable for continued service. See pictureof a typical example of chevron cutting in the tread photo section at the right.

Preventive2Maintenance

15

BEFORE MOUNTINGCorrect mounting and demounting of aircraft tires and tubes are essential for maximum safety and economy.It is a specialized job that should be done with the proper tools and careful attention to specific instructionsand established procedures.

BIAS AND RADIAL AIRCRAFT TIRE GUIDELINESRadial aircraft tires may exhibit different characteristics than bias aircraft tires when operated under similarconditions. The following guidelines are recommended:

1. The airframe must be certified for use of radial tires in place of bias or vice versa. Questions concerningthe certification of a given aircraft must be referred to the airframe manufacturer.

2. Radial aircraft tires should not be mounted on wheels designed for bias ply tires or bias tires on wheelsdesigned for radial tires without first checking with the wheel manufacturer.

3. It is acceptable to mount bias tires on nose positions and radial tires on main positions, or vice versa, onthe same aircraft.

4. For Return to Base Operation Only: In case a tire replacement is needed in a remote location, the position may be filled with an appropriate tire of the other construction for return to base operation only.

WARNING

Aircraft tires are designed to be operated up to or at rated inflation pressure. Greatly exceeding these pressures may cause the aircraft wheel or tire to explode, which can result in serious or fatal injury.Pressure Regulators should always be used to help prevent injury or death caused by over-pressurization of the tire assembly. Maintenance and use of pressure regulators should be performed inaccordance with the manufacturer’s instructions. The safety practices for mounting and demountingaircraft tires referenced in the aircraft and wheel manufacturers maintenance manuals should be followed.

Newly assembled tires and wheels should be inflated in safety cages.

AIRCRAFT WHEELSAircraft wheels made today, for tube-type and tubeless tires, are the split wheel or demountable flange variety. While this makes the job of mounting and demounting physically easy, strict attention to detail isrequired.

Wheel Manufacturer’s InstructionsSpecific instructions on modern wheels are contained in maintenance manuals available from the aircraftmanufacturer or directly from the wheel manufacturer. It is inadvisable to mount or demount aircraft tireswithout the specific information contained in these manuals. In addition, refer to airframe manufacturer’smanual on use of incline ramps and/or jacks for maintenance purposes.

Safety Precautions With WheelsAn inflated tire/wheel assembly is a potentially explosive device. Mounting and demounting of aircraft tires is a specialized job that is best done with the correct equipment and properly trained personnel. The following precautions are advisable in handling both tube-type and tubeless tires.

Mounting andDemounting 3

16

Mounting and3Demounting

BEFORE MOUNTING (CONT’D)

AIRCRAFT TIRE CONDUCTIVITYUnder certain circumstances (for example during refueling), operators have concerns relative to the dissipation of static electricity for aircraft.

In those situations where buildup of static electricity is of concern, it is important that mechanical meansalways be used to ground the aircraft.

CAUTIONDo not rely on tires to dissipate static electricity.

MATCHING DUAL TIRESWhen new and/or retreaded tires are installed on the same landing gear axle, the diameters do not have to be matched, as long as the dimensions are within the Tire and Rim Association inflated dimensional tolerances for new and grown tires. This will insure that both tires will carry an equal share of the axle load.

Data for new tire diameters after a 12 hour stretch period, at rated inflation pressure, are available inGoodyear’s Aircraft Tire Data book. The maximum grown diameter is calculated using Tire and Rim orETRTO formulas, and these formulas are also found in Goodyear’s Aircraft Tire Data book. If help is needed with these calculations, please contact your local Goodyear representative.

MOUNTING PROCEDURES

IMPORTANT - INFLATION PRACTICES

(See Section 2, Proper Inflation Procedures)

1. CHECK DAILY WHEN TIRES ARE COOL2. INFLATE TO WORST CONDITIONS 3. USE DRY NITROGEN GAS (SAFELY)4. INCREASE PRESSURE 4% FOR TIRES UNDER LOAD5. ALLOW 12 HOUR STRETCH AFTER MOUNTING6. NEVER REDUCE THE PRESSURE OF A HOT TIRE

REMEMBER - 1% PRESSURE CHANGE FOR 5°F (3° C) 7. EQUAL PRESSURE FOR DUALS8. CALIBRATE INFLATION GAUGE REGULARLY

WARNING Failure to comply with the following instructions may cause tire/tube/wheel failure and serious injury.

MOUNTING PROCEDURES (CONT’D)Bead lubrication in mounting both tubeless and tube-type tires is often desirable to facilitate mounting andseating of the beads against the wheel flanges. A light coat of talc can be used. Use the following guidelinesfor mounting:

• Use a clip-on chuck, an extension hose, and a safety cage for inflation. • Use a direct reading or dial type pressure gauge with 5 psi increments that is calibrated on a regular basis. • When inflating a tire/wheel assembly, regulate the supply line to a pressure no more than 50% higher

than the tire service pressure.• Do not inflate a tire above rated pressure to seat beads.

TUBE-TYPE• Use the correct tire and tube for the wheel assembly.• Clean inside of tire, then lubricate lightly with talc.• Inflate tube to slightly round, and insert in tire.• Align yellow stripe on tube with red balance dot on tire. Align red dot with valve if no stripe on tube.• When mounting tire and tube on wheel, be sure that wheel bolts are torqued to wheel manufacturer’s

instructions before inflating.• Inflate tire in a safety cage to rated pressure.• Deflate assembly to equalize stretch.• Reinflate to rated pressure.• After 12 hour stretch period, reinflate to rated inflation pressure.

Within the next 24 hours, if the pressure decreases more than 5%, it could be caused by trapped air betweenthe tire and tube, valve core leakage, or a damaged tube.

NOTE: Check inflation pressure prior to each flight.

Tube InspectionSince there are three reasons for air loss in a tube-type tire (a hole in the tube, a defective valve stem or valvecore), finding an air leak is usually simple. The first step is to check the valve and tighten or replace the coreif it is defective. If the valve is airtight, demount the tire, remove the tube, locate the leak (by immersion inwater if necessary). Replace the tube.

CAUTIONFor inspection use only enough pressure to round out tube. Excessive inflation strains splices and maycause fabric separation of reinforced tubes.

Reuse Of TubesA new tube should be used when installing a new tire. Tubes grow in service, taking a permanent set ofabout 25% larger than the original size. This makes a used tube too large to use in a new tire, which couldcause a wrinkle and lead to tube failure.

TUBELESS TIRESA new O-ring seal with the correct part number should be used at each tire change following the wheelmanufacturer’s specifications.

• Check for word “Tubeless” on sidewall.• Make sure tire is clean inside.• Clean the bead base with a cloth dampened with denatured alcohol. Allow bead seat area to dry.• Align red balance dot on the tire with wheel valve or wheel heavy point (if indicated on wheel). If no red

dot appears on the tire, look in the liner for a balance pad. Align this area to the valve or heavy spot onthe wheel. If no balance pad is in the tire, then align the tire serial number to the valve or heavy spot onthe wheel.

• Be sure that wheel bolts are properly torqued per the wheel manufacturer’s instructions.• Inflate tire in a safety cage using dry nitrogen to rated pressure.• After 12-hour stretch period, reinflate to rated inflation pressure with dry nitrogen.


17

18


MOUNTING PROCEDURES (CONT’D)

If pressure drops more than five percent (5%) in the next 24 hours:• Check with water or soap solution for loose or defective valve, valve core, valve seal, fuse plug, pressure

release plug, O-ring seal, wheel base and flanges.• If no leaks are found, rerun 24 hour diffusion check. If pressure still drops more than 5%, disassemble

tire/wheel assembly.• Check wheel O-ring seal for condition, proper size and type, and lubricant.• Check wheel for cracks, porosity, fuse plug or pressure release plug malfunction.

TUBES IN TUBELESS TIRESA Goodyear tubeless aircraft tire can be used (with a tube) in place of the same size tube-type tire if the tube -type tire has the same or lower speed and ply ratings. Ensure that any manufacturing stickers on the tireinnerliner are removed to prevent damage to the tube. When the tube and tubeless tire are initially mounted some air may be trapped between the tire and tube. Since tubeless tires have much thicker innerliners than tube-type tires, any air trapped will take longer to escape and will slowly reduce the inflation pressure as it does so. During the first two weeks after mounting, monitor the inflation pressurecarefully and reinflate as required.

INFLATION PRESSURE LOSS IN TUBELESS ASSEMBLIESSince there are many causes for inflation pressure loss with a tubeless assembly, a systematic troubleshootingapproach is advisable for minimum maintenance costs. Moreover, when chronic but not excessive inflationpressure loss exists, other factors such as inaccurate gauges, air temperature fluctuations, changes in maintenance personnel, etc., may be the source. If a definite physical fault is indicated, a troubleshootingprocedure similar to the one outlined below is recommended. (See wheel manufacturer’s maintenance/overhaul manual for details pertaining to specific wheels.)

ValveBefore deflating and removing tire, check the valve. Put a drop of water or soap solution on the end of thevalve and watch for bubbles indicating escaping pressure. Tighten valve core if loose. Replace valve core ifdefective and repeat leak test to check. Check the valve stem and its mounting for leaks with a soap solution. If a leak is detected, deflate the tire/wheel assembly and replace the valve core and/or valveassembly. Make certain that every valve has a cap to retain inflation and prevent dirt, oil, and moisturefrom damaging the core.

Fusible PlugThe fusible plug may also be defective or improperly installed. Use a soap solution to check fusible plugsfor leaks before removing tire. Leaks can usually be pinpointed to the plug itself (a poor bond between thefusible material and the plug body) or to the sealing gasket used. Be sure the gasket is one specified by thewheel manufacturer and that it is clean and free of cuts and distortion.

If excessive heat has caused a fusible plug to blow, the tire may be damaged and should be replaced. After a fuse plug in a wheel blows, the wheel should be checked for soundness and hardness in accordance withthe applicable wheel maintenance/overhaul manual. If the tire has not rolled, it can be sent to a retreaderfor inspection and retreading.

INFLATION PRESSURE LOSS IN TUBELESS ASSEMBLIES(CONT’D)

Release PlugThe inboard wheel half may contain a pressure release plug, a safety device that prevents accidental overinflation of the tire. If the tire is overinflated, the pressure release plug will rupture and release the tirepressure. A soap solution can be used to check a release plug to determine whether or not it is defective.

Wheel BaseGas escaping through a cracked or porous wheel base is usually visible in an immersion test. Consult thewheel manufacturer’s manual for rim maintenance and repair.

O-Ring SealA defective o-ring seal can usually be detected in an immersion test. Check to see that wheel bolts are properly torqued.

Beads And FlangesCheck the bead and flange areas of a tire for leaks before demounting. This can be done either by immersion or by using a soap solution. Any of the following factors can cause gas loss:

• Cracks or scratches in wheel bead ledge or flange area.• Exceptionally dirty or corroded wheel bead seating surfaces.• Damaged or improperly seated tire bead.

Tire CarcassBefore demounting, use an immersion test or soap spray to determine if the tire itself has a puncture. If apuncture is found in the tread or sidewall, the tire must be scrapped.

Casing Vents (Weep Holes)All tubeless tires have been vented in the lower sidewall area. These vents prevent separation by relievingpressure buildup in the casing plies and under the sidewall rubber. These vent holes (marked by green dots)will not cause undue pressure loss and do not close. Covering them with water or a soap solution may showan intermittent bubbling, which is normal.

Pressure Retention TestWhen no leaks can be found on the prior checks, a pressure retention test must be performed. The tireshould be inflated to operating pressure for at least 12 hours before starting the test. This allows sufficienttime for the casing to stretch, but can result in apparent inflation pressure loss. The tire must be reinflatedafter the stretch period to operating pressure. Allow the tire to stand at constant temperature for a 24-hourperiod and recheck pressure.


19

WHEEL SPLIT

FUSIBLE PLUG VENT

BEAD SEAT AREA

WHEEL FLANGEWHEEL FLANGE

VALVE

BEAD SEATAREA

SPLIT RIM WHEELDEMOUNTABLE

FLANGE RIM

•

•

• •

20


TIRE BALANCING AND LANDING GEAR VIBRATIONIt is important that aircraft wheels and tires be as well balanced as possible. Vibration, shimmy, or out ofbalance is a major complaint. However, in most cases, tire balance is not the cause.

Other factors affecting balance and vibration are:• Flat-spotted tire due to wear and braking • Out of balance wheel halves • Installation of wheel assembly before full tire growth• Improperly torqued axle nut • Improperly installed tube • The use of non aircraft tubes• Improperly assembled tubeless tire • Poor gear alignment • Bent wheel • Worn or loose gear components • Incorrect balancing at wheel assembly

In addition, pressure differences in dual mounted tires and incorrectly matched diameters of tires mountedon the same axle may cause vibrations or shimmy.

With some split wheels, the light spot of the wheel halves is indicated with an “L” stamped on the flange.In assembling these wheels, position the “L’s” 180 degrees apart. If additional static balancing is requiredafter tire mounting, many wheels have provisions for attaching accessory balance weights around the circumference of the flange.

AIRCRAFT TIRE/WHEEL BALANCER FOR GENERAL AVIATION OPERATION

Balancing instructions for this tire/wheel balancer can be obtained from Desser Tire & RubberCompany: 800-AIR-TIRE (800-247-8473).

NOTE: The T.J. Karg Company tire/wheel balancer is no longer available.

21


DEMOUNTING CAUTION

A tire/wheel assembly that has been damaged in service should be allowed to cool for a minimum of three (3) hours before the tire is deflated.

The two types of demounting equipment used are “full-circle” and “semi-circle” bead breakers. With bothtypes of bead breakers, the desired procedures are a combination of pressing against the tire sidewalls closeto the edge of the wheel flanges and controlling the lateral movement of the bead breaker rings after con-tacting the tire sidewalls. This procedure assures the maximum lateral force against the tire to demount itwithout internal tire damage or kinking the tire beads.

1. Prior to demounting the tire from the wheel, it should be completely deflated with a deflation cap.

2. After all the pressure has been relieved, remove the valve core. Remember that valve cores still underpressure can be ejected like a bullet. If wheel or tire damage is suspected, approach the tire from thefront or rear, not from the side (facing the wheel).

3. Leave the wheel tire bolts tight until after unseating the tire beads. If the bolts are loosened or removedbefore unseating the tire beads, the wheel mating surfaces may be damaged.

4. If “full-circle” type bead breaking equipment is used, the appropriate bead breaker flange ID should beapproximately 1 inch larger than the aircraft flange OD. For example, an H40x14.5-19 tire is mountedon a 19 inch diameter wheel with a 1.4 inch flange. So, 19 inch wheel diameter plus twice the wheelflange height of 1.4 inches plus the 1 inch clearance adds up to 22.8 inches, which is rounded to give abead breaker flange ID of 23 inches. Also, the bead breaker flanges should be equipped with rubber or plastic pads to prevent lateral movement after contacting and compressing each tire sidewall approximately 1.5 inches and to prevent damage to the aircraft wheel.

5. If “semi-circle” type bead breaking equipment is used, the same press tools are used for all size tires, butthe press tools are raised or lowered to position them for each tire at the level of the center of the wheeland as close to the wheel OD as possible. This type of bead breaking equipment is equipped with sensors that prevent lateral movement after the press tools have compressed the tire approximately 3.5inches (1.75 inches per side) and contacts the wheel. The tire can be turned on the bead breaker rollersand the breaking action repeated until the tire beads are unseated

22

INSPECTING MOUNTED TIRESSystematic inspection of mounted tires is strongly recommended for safety and tire economy. The frequencyof the inspection should be determined by the use and normal tire wear of the particular aircraft involved.With some aircraft, tire inspection after every landing or at every turnaround is required. With all aircraft, athorough inspection is advisable after a hard landing.

Treadwear Inspect treads visually and check remaining tread. Tires should be removed when tread has worn to the baseof any groove at any spot, or to a minimum depth as specified in aircraft T.O.’s.

Return To Base LimitsGoodyear tires can remain in service with visible cord in the tread area only as long as the top fabric layer is not worn through or exposed for more than 1/8 of the circumference of the tire, and not more than oneinch wide. Tires within these limits can continue in service no longer than necessary to return to a maintenancebase and be replaced. (This applies to the proper tires for the aircraft as specified in its Aircraft MaintenanceManual.) For all other circumstances, normal removal criteria are still recommended as per the rest of this manual. This does not apply to military tires with Maximum Wear Limits marked on the sidewall.NOTE: Further use of tires beyond this point may render a tire unsafe or unretreadable.

Uneven WearIf tread wear is excessive on one side, the tire can be demounted and turned around, providing there is noexposed fabric. Gear misalignment causing this condition should be corrected.

Tread Cuts Inspect tread for cuts and other foreign object damage and mark with crayon or chalk. Follow the removalcriteria below:1. Follow specific cut removal criteria from Aircraft Maintenance manuals, Operation manuals, or tire cut

limits on the tire sidewall when available. 2. When specific cut removal criteria are not available use the following Goodyear removal criteria: any cut into the

casing plies on bias tires, any cut into the belt package on radial tires, any cut which extends across one or morerubber tread ribs to the fabric, rib undercutting at the base of any cut.

WARNINGDo not probe cracks, cuts or embedded foreign objects while tire is inflated.

Sidewall DamageRemove tire from service if weatherchecking, cracking, cuts and snags extend down to the casing ply in thesidewall and bead areas. Cuts and cracks deeper than one ply require the tire to be scrapped.

BulgesBulges in any part of tire tread, sidewall or bead area indicate a separation or damaged tire. Mark with crayon and remove from service immediately.

Fabric Fraying/Groove CrackingTires should be removed from service if groove cracking exposes fabric or if cracking undercuts tread ribs.

Flat SpotsGenerally speaking, tires need not be removed because of flat spots due to touchdown and breaking orhydroplaning skids unless fabric is exposed. If objectionable unbalance results, however, rebalance theassembly or remove the tire from service.

Casing Flat SpottingLoaded tires that are left stationary for any length of time can develop temporary flat spots. The degree ofthis flat spotting depends upon the load, tire deflection and temperature. Flat spotting is more severe andmore difficult to work out during cold weather. Under normal conditions, a flat spot will disappear by theend of the taxi run.

Radial Tire Sidewall IndentationRemove from service with 3mm or greater sidewall indentation.

Inspection,4Storage and Shipping

Inspection,Storage and Shipping 4

23

BeadsInspect bead areas next to wheel flanges for damage due to excessive heat, especially if brake drag or severebraking has been reported during taxi, take-off or landing. If damaged, remove tire from service.

Tire ClearanceLook for marks on tires, gear, and in wheel wells that might indicate rubbing due to inadequate clearance.

WheelsCheck wheels for damage. Wheels that are cracked or damaged should be taken out of service for repair orreplacement in accordance with manufacturer’s instructions.

Inflation Pressure Loss In Tire/Wheel AssembliesRefer to section on MOUNTING for a complete review of these procedures.

TYPICAL TREADWEAR PATTERNS

NORMAL

Even treadwear on this tire indicates that it has been properly maintained and run at correct inflation pressure.

EXCESSIVE

Worn to the breaker/casing plies, the tire should not be left in service or retreaded.

ASYMMETRICAL WEAR

Some aircraft tires exhibit faster shoulder wear on one shoulder versus the other due to non-tire influences (camber-type wear, etc.). If this condition exists, the

tire’s life can be extended by demounting and reversing (“flipping”) the tire on the wheel as long as tire wear limit and the physical condition criteria are satisfied.

NOTE: “FLIPPING” MUST NOT BE DONE ON SINGLE CHINE TIRES.

STEPWEAR

This is a normal wear pattern on some tires, particularly H-type tires. Can be caused or worsened by underinflation.

24


TREAD CONDITIONS

CutsPenetration by a foreign object. See Section 4,Inspection, Storage and Shipping; Inspecting MountedTires; Tread Cuts.

Spiral WrapSome retreads have reinforcing cords wound into thetread which become visible as the tire wears. This is anacceptable condition and not cause for removal. The wrap reduces chevron cutting and tread chunking.

Tread ChunkingA condition in the wearing portion of tread usuallydue to rough or unimproved runways. Remove iffabric is visible.

Tread SeparationA separation or void between components in thetread area due to loss of adhesion, usually caused byexcessive loads or flex heating from underinflation.Remove immediately.


25

TREAD CONDITIONS (Cont’d.)

Groove CrackingA circumferential cracking at the base of a tread groove; remove if fabric is visible. Can result fromunderinflated or overloaded operation, or improperstorage conditions.

Rib Undercutting An extension of groove cracking progressing under a tread rib; remove from aircraft. Can lead to tread chunking, peeled rib or thrown tread.

Peeled RibUsually begins with a cut in tread, resulting in a circumferential delamination of a tread rib, partially ortotally, to tread reinforcing ply. Remove from aircraft.

Thrown TreadPartial or complete loss of tread down to tread fabricply or casing plies. Remove from aircraft.

26


TREAD CONDITIONS (Cont’d.)

SkidAn oval-shaped flat spot or skid burn in the tread rubber. May extend to or into fabric plies. Remove ifbalance is affected, fabric is exposed, or tire is ruptured.

Tread Rubber Reversion

An oval-shaped area in the tread similar to a skid, butwhere rubber shows burning due to hydroplaning during landing usually caused by wet or ice-coveredrunways. Remove if balance is affected.

Open Tread SpliceA crack in the tread rubber where the joint (splice) separates in a radial (sideways) direction. Tires withthis defect should be removed from service.

Chevron CuttingTread damage caused by running and/or braking oncross-grooved runways. Remove if chunking to fabricoccurs or tread cut removal criteria are exceeded.


27

SIDEWALL CONDITIONS

Cut or SnagPenetration by a foreign object on runways and ramps,or in shops or storage areas. Remove from aircraft ifinjury extends into fabric.

Ozone or Weather Checking/CrackingRandom pattern of shallow sidewall cracks usuallycaused by age deterioration, prolonged exposure toweather, or improper storage. Remove from aircraft iffabric is visible.

Radial or Circumferential CracksCracking condition found in the sidewall/shoulderarea; remove from aircraft if down to fabric. Can resultfrom underinflated or overloaded operation.

Sidewall SeparationSidewall rubber separated from the casing fabric.Remove from aircraft.

28


BEAD CONDITIONS

CASING CONDITIONS

Brake Heat DamageA deterioration of the bead face from toe to wheelflange area; minor to severe blistering of rubber in thisarea; melted or solidified nylon fabric if temperatureswere excessive; very hard, brittle surface rubber. Tire isto be scrapped.

Kinked BeadAn obvious deformation of the bead wire in the beadtoe, face or heel area. Can result from improperdemounting and/or excessive spreading for inspectionpurposes. Tire is to be scrapped.

Inner Tire BreakdownDeterioration (distorted/wrinkled rubber of tubelesstire innerliner or fabric fraying/broken cords in tube-type) in the shoulder area usually caused byunderinflated or overloaded operation. Tire is to be scrapped.

Impact BreakRupture of tire casing in tread or sidewall area, usuallyfrom extremely hard landing or penetration by foreignobject. Tire is to be scrapped.


29

TIRE AND TUBE STORAGEIdeally, both new and retreaded tires should be stored in a cool, dry place out of direct sunlight.Temperatures should be between 32°F (0°C) and 85°F (30°C). Particular care should be taken to storetires away from fluorescent lights, electric motors, battery chargers, electric welding equipment, electric generators and similar equipment. These items create ozone, which has a deteriorating effect on rubber.

Care should be taken that tires do not come in contact with oil, gasoline, jet fuel, hydraulic fluids or similarhydrocarbons. Rubber is attacked by these in varying degrees. Be particularly careful not to stand or lay tireson floors that are covered with these contaminants.

All tires and tubes should be inspected immediately upon receipt for shipping and handling damage.

Whenever possible, tires should be stored vertically on tire racks. The surface of the tire rack against whichthe weight of the tire rests should be flat and wide to minimize distortion.

Axial (circumferential) rotation of unmounted, vertically stored tires should not be required. With respectto the effect of storage time on rotation, we strongly suggest the use of first-in first-out (FIFO) storage. Thishelps to avoid overage, distortion and related field issues.

Stacking of most tires is permissible; however, care must be used to prevent distortion of the tires on thebottom of the stack. To prevent chine distortion, stacking chine/water deflector tires is not recommended.Tires stored in racks, but leaning on the chine, can also cause distortion. The following is the maximumrecommended stacking height:

Maximum RecommendedTire Diameter Stacking Height

Up to 40 inches 5Over 40 inches to 49 inches 4

Over 49 inches 3

Tubes should be stored in their original cartons whenever possible. If stored without their cartons, theyshould be lightly lubricated with talc powder and wrapped in heavy paper.

Tubes can also be stored in matching tires. Tires should be clean and lightly lubricated with talc with tubesinflated just enough to round them out.

Under no circumstances should tubes be hung over nails, pegs or any object that might form a crease in thetube. Such a crease will eventually produce a crack in the rubber.

TIRE AND TUBE AGE LIMITAge is not a proper indicator of tire serviceability. Goodyear aircraft tires or tubes have no age limit restriction regardless of calendar age as long as all service criteria (Section 2 of this manual), visual criteria(Section 4), or individual customer-imposed restrictions are met.

Tubes are not reusable; they can grow as much as 30% in service. Reusing them can result in folded,pinched tubes which can fail or create an imbalance.

30


STORAGE OF MOUNTED ASSEMBLIESSet the pressure at operational pressure for the desired tire. The assemblies can be stored like this for up to12 months. After that time, inflated assemblies that have not been used should be re-inspected by a qualified inspector. However, to maximize tire life, it is recommended to rotate inventory on a first-in-first-out (FIFO) basis.

The above inspections can be performed multiple times as long as the tire meets all inspection and inflationcriteria. If these criteria cannot be met, the tire should either be scrapped or returned for retreading,depending on the defect found. For assemblies stored for extended periods of time, air retention checksshould be performed to help re-verify the airworthiness of the assembly. Prior to putting the assembly inservice, if nitrogen was not used for storage inflation, deflate the assembly and re-inflate with nitrogen (per industry standards).

These recommendations do not supersede local storage facility regulations, ground transportation restrictions, or prevailing aviation authority requirements. Depending on local regulations, it may be theoperator’s responsibility or that of the tire handler (shipping or storage) to ensure compliance with therequirements for the locations in which they operate, transport, and store mounted tire assemblies.

SHIPPINGSHIPPING INFLATIONTransportation of a serviceable aircraft tire/wheel assembly should be in accordance with the applicable regulatory body for the airline.

Transportation of a serviceable inflated aircraft tire is covered by the U.S. Department of TransportationCode of Federal Regulations, the International Air Transport Association (IATA), and other regulatory bodies.

While serviceable tires may be shipped fully pressurized in the cargo area of an aircraft, Goodyear’s recommendation is to reduce pressure to 25% of operating pressure or 3 bars / ~40 psi, whichever is the lesser. Reinflate to operating pressure before mounting on the aircraft.

SHIPPING AND HANDLING DAMAGEIn Goodyear’s manufacturing facilities, stringent finished tire inspection is performed to help ensure thatGoodyear tires are shipped to the customer in first class condition. Because of the characteristics of rubber,special care is taken to inspect shipping containers, pallets and trucks for obvious conditions that couldcause damage to these tires. However, aircraft tires may be damaged during shipping or handling after thetires leave the control of our facilities and prior to entering service. Damage of this nature is the responsibilityof the freight carrier and needs to be handled between the receiving facility and the freight handler as soonas possible after receipt of the tire(s). The reader should keep in mind that some of this damage can be soslight that it escapes incoming inspection procedures and is noticed later or after the tire is mounted on thewheel assembly and inflated.

Cuts and snags can occur on tread areas, sidewalls and bead areas of tires. In many cases these cuts arecaused by nails, wood, splinters, utility knives, forklift tines or sharp metal objects in transport trailers.

31

RETREADING TIRESGoodyear has been retreading aircraft tires since 1927. Today, most military and commercial airline tiresare designed to be retreaded. Retreading an existing casing can provide more landings per tire at a lower costper tread, giving a significantly lower overall operating cost.

As with new tires, retreads must pass airworthiness authority testing requirements. Inspection techniques,such as air injection, holography and shearography, ensure that used casings and the final retread meet allspecifications. Again, as with new tires, retread materials and components are certified by quality assurancestandards.

The following is a scenario of the retread process:

• Tires are received and assigned a process card and number that follows the tire throughout the completeprocess. All pertinent information is entered into a computer database.

• Tires are visually inspected and air needle pressure tested to reveal any separations or possible liner leaks.• Tires are put into hot storage to shrink the nylon casing back to its original shape.• Tires are then placed on a buffing machine with the casing under pressure to ensure roundness. • The old tread is buffed off the casing along with any removable fabric reinforcement plies.• New fabric reinforcement plies are applied, as required, along with the new tread rubber. • Tires are then placed in a mold and the new tread materials are vulcanized (cured).

Along with the standard visual and air needle inspections, a major part of the Goodyear retread inspectionprocess includes Holography or Shearography inspections.

Shearography InspectionGoodyear uses shearography equipment as part of its state-of-the-art nondestructive inspection methods. It is capable of detecting very small anomalies that could affect tire performance. Its advantages are real-time inspections through CRT screen viewing and video data storage. It has the capability of bead-to-bead inspection.

Retreading 5

32

It is helpful to have some knowledge of aircraft tire properties to better understand some of the charts andgraphs presented in this section. Some of the main properties are discussed on the following pages.

The major design philosophy of an aircraft tire, as compared to other tire types such as passenger and trucktires, is that they are designed for intermittent operation. Because of this design feature and to allow thelowest possible ground bearing pressure, the aircraft tire operates at much higher deflections than other tire types.

The Tire and Rim Association (T&RA) and European Tire and Rim Technical Organization (ETRTO) wereestablished so that different manufacturers’ tires and wheels (rims) would be interchangeable. Tire sizenomenclature has changed throughout the years due to ever increasing technology. The T&RA and ETRTOalso establish the load and pressure ratings of a given size tire.

TIRE NAME SIZE CLASSIFICATION Three Part Type All new sizes being developed are in this classification. This group was developed

to meet the higher speeds and loads of today’s aircraft. Note: Some sizes have a letter such as “H” in front of the diameter. This is to identify a tire that is designedfor a higher percent deflection.

Metric Type This size designation is the same as Three Part except the diameter and sectionwidth dimensions are in millimeters, and the wheel/rim diameter is in inches.

Type VII This type covers most of the older sizes and was designed for jet aircraft with itshigher load capacity.

Type III This type was one of the earliest size designations used for piston-prop type aircraft. Its characteristic is low pressure for cushioning and flotation.

Radial Radial size nomenclature is the same as Three Part except an “R” replaces the “-” (dash) before the wheel/rim diameter.

Tire Tire Size Nominal Nominal NominalName Example Diameter Section Wheel/RimType Width Diameter

Three Part H49x19.0-22 49 19.0 22Metric 670x210-12 670 (mm) 210 (mm) 12 (in)

Type VII 49x17 49 17Type III 8.50-10 8.50 10Radial 32x8.8R16 32 8.8 16

For a complete listing of tire sizes and aircraft applications along with some engineering design parameters,Goodyear publishes another book titled Aircraft Tire Data Book. Contact your local Goodyear representativeto receive a copy.

Aircraft Tire6 Properties

Aircraft TireProperties 6

33

Tire Comparison Aircraft - vs - Passenger

PARAMETER AIRCRAFT PASSENGER

Size 27 x 7.75-15 P205/75R15Diameter (in) 27.0" 27.1"Section Width 7.75" 7.99"

Ply Rating 12 –Load Rating 9650 1598

Pressure 200 35Deflection 32% 11%Max Speed 225 112

Load/Tire Weight 244 78

TRUCK

INDUSTRIALOFF THE ROAD

PA

SSEN

GER

AIRCRAFT TIRES

SPEE

D (

MP

H)

RA

CE

300

200

100

0

10,000 20,000 30,000 40,000 50,000 60,000

AIRCRAFT TIRE -VS- OTHER TIRE APPLICATIONSMany people believe that all tires are alike. This chart shows a comparison of an aircraft tire versus a passenger tire. The tires may be similar in size, but that is where similarities end.

Comparing, in particular, the LOAD and SPEED ratings of these two tires, the aircraft tire carries 9650 lbs.,which is approximately six times the passenger tire load of 1598 lbs. It is also traveling over twice as fast.

Also, notice that the operating pressure of the aircraft tire is almost 6 times that of the passenger tire; and that the aircraft tire is operating at a deflection of 32%, as compared to 11% for the passenger tire.

Aircraft Tires -vs- Other Tires ApplicationsThe HEAVY LOAD coupled with the HIGH SPEED of aircraft tires makes for extremely SEVERE OPERATING CONDITIONS. Several of the following charts are centered around these two major factors.The purpose of these charts is to present items that minimize and maximize these adverse effects. The ultimate goal is to not only understand what needs to be done, but why.

TIRE OPERATING RANGES OF OTHER APPLICATIONSLOAD AND SPEED RANGES

This chart shows the SPEED versus LOAD operating ranges of passenger, truck, race, farm, off-the-road, andaircraft tires. Only Aircraft tires have the worst of both loads and speeds. This means that maintenancepractices and operating techniques that work fine for passenger tires are not acceptable for aircraft tires.Because of the severe conditions under which aircraft tires operate, any deviation from proper techniquesand practices will have severe consequences.

34

CENTRIFUGAL FORCECENTRIFUGAL FORCE is combination of LOAD & SPEED

Both heavy loads and high speeds contribute to the strong centrifugal forces acting on an aircraft tire. Therelationship of speed versus centrifugal force is obvious. The effect of coupling speed with a heavy load isshown in the drawing below.

This drawing depicts a tire rotating counterclockwise. The heavy solid horizontal line represents the groundor runway. The distance “CX” is half the footprint length. Because the tire is pneumatic, it deflects whencoming into contact with the ground. This deflection is represented by the distance “BC” or “XZ”. In thesame length of time that a point on the surface of the tire travels the last half of the footprint “CX”, it mustalso move radially outward the distance “ZX”.

As the tire leaves the deflected area, it attempts to return to its normal shape. Due to centrifugal force andinertia, the tread surface doesn’t stop at its normal periphery but overshoots, thus distorting the tire from itsnatural shape. This sets up a traction wave in the tread surface.

TIRE LEAVING CONTACT AREA

ROTATION NORMAL PERIPHERY

TRACTION WAVE

A B

C

Z

X

Effects of7Operating Conditions

Effects ofOperating Conditions 7

35

CENTRIFUGAL FORCE (CONT’D)

TRACTION WAVEThis photograph shows just how severe a traction wave can become under certain operating conditions.

The following parameters help explain the magnitude of forces acting on the tire carcass and tread as it runson a test dynamometer.

At this speed, it takes only 1/800 of a second to travel 1/2 the length of the footprint (CX). In that sametime, the tread surface must move radially outward 1.9 inches. This means an average radial acceleration of200,000 ft./sec./sec. That’s over 6,000 G’s!

This means the tread is going through 12,000 to 16,000 oscillations per minute.

Obviously, a tire cannot withstand this type of punishment. How can a traction wave be reduced oreliminated? In other words, what factors affect the traction wave? The following page shows effects ofSPEED and UNDERINFLATION.

Speed 250 MPH

Revolutions per Minute 4,200

Deflection 1.9 inches

36

CENTRIFUGAL FORCE (CONT’D)

Traction Wave -vs- Speed

40X14 24 PR @ Rated Pressure

The above photographs show the tread of a tire as it leaves the footprint moving toward the reader. The only test variable is speed, showing from left to right 190, 210, 225 mph. The higher the speed, the morepronounced the traction wave.

One of the major tasks of the tire design engineer is to minimize this traction wave at the required speedsand loads.

Traction Wave -vs- Underinflation

40X14 24 PR 225 MPH

All tires in the above photographs are traveling at 225 mph. In the picture to the far left there is noappreciable traction wave because the tire is properly inflated. The only test variable is pressure, showingfrom left to right rated pressure, -10 psi, -15 psi, -20 psi. Obviously, the greater the underinflation, the morepronounced the traction wave.

Note how the grooves open and close as the tread passes through the traction wave.



37

CENTRIFUGAL FORCE (CONT’D)The centrifugal forces that generate a traction wave, combined with the thousands of revolution cycles, cancause tread problems such as Groove Cracking and Rib Undercutting, which could result in tread loss.

GROOVE CRACKING is a circumferential crack that can develop inthe base of the groove caused by the repeatedflexing of the groove when a traction wave ispresent. Tires should be inspected frequentlyand removed if any fabric is visible.

RIB UNDERCUTTINGis normally a continuation of the groovecracking that continues under the tread ribbetween the rubber and the tread reinforcingfabric.

Rib undercutting can progress to a point where pieces of the rib or the whole rib can become separatedfrom the carcass. In severe cases the complete tread can come off the carcass. Progression from deep groovecracks to undercutting and ultimate tread loss can occur rather quickly. Therefore, careful examination ofthe tires before each take-off is extremely important. The tire should be removed if the fabric is exposed.

Before leaving the subject of centrifugal force, it is interesting to look at the magnitude of these forces dueto speed only, disregarding other radial accelerations caused by loads and deflections. This chart shows thecentrifugal forces acting on one ounce of tread rubber on a 30-inch diameter tire.

Centrifugal Forces 30-Inch Diameter Tire

The force increases as the square of the speed from 500 Gs, or 33 lbs. per ounce, at 100 mph, to an extremeof 8000 Gs, or 528 lbs. per ounce, at 400 mph.

An average tread for this size tire would weigh approximately 8 lbs. This means that the effective weight ofthe total tread at 200 mph would be 16,600 lbs. and at 400 mph would be 67,500 lbs.

With forces like these, it is amazing that a tread can stay on a tire at all.

MPH Gs FORCE ON 1 OZ FORCE ON TOTAL OF TREAD TREAD (8 LBS)

100 500 33 LBS 4,000 LBS

200 2000 130 LBS 16,600 LBS

300 4500 300 LBS 38,500 LBS

400 8000 528 LBS 67,500 LBS

38

HEAT GENERATIONAs severe as the effects of these high centrifugal forces are, HEAT has a more detrimental effect. HEAVYLOADS and HIGH SPEEDS cause HEAT GENERATION in aircraft tires to exceed that of all other tires.

To understand the magnitude of heat generated in typical aircraft tires, several test tires were fitted withtemperature sensors, or thermistors, mounted at the locations indicated. The actual temperature rise duringa variety of free-rolling taxi tests was monitored and recorded. The following charts show the effect of taxispeed, inflation pressure, and taxi distance on internal heat generation for typical main landing gear tires.

THERMISTORS



39

HEAT GENERATION (CONT’D)

The vertical dotted line at 35 mph (30 knots) indicates the recommended maximum taxi speed. Onthe above chart, the curves constantly slope upward with higher taxi speeds. In other words, the fasteran aircraft travels over a given distance, the hotter the tires will become.

Many people would expect the shoulder area to generate the most heat. In reality, the bead and lowersidewall area are the hottest. There are two major reasons for this:

1. All forces, in or acting on a tire, ultimately terminate at the bead. This is an area of high heatgeneration.

2. Rubber is a good insulator; or said another way, it dissipates heat slowly. The bead area, being thethickest part of the tire, retains the heat longer than any other part of the tire.

A

This tire was designed to be operated at 32% deflection, as the vertical dotted line indicates. Left ofthis line designates overinflation, and to the right underinflation. When the speed and the distancetraveled are constant, the more a tire is underinflated the hotter it becomes.

The rate of temperature rise versus underinflation is the highest in the shoulder area due to increasedflexing. The bead area, however, still remains hottest.

B

TEMPERATURE RISE VS TAXI SPEED

TEM

PER

ATU

RE

RIS

E ˚F

250

200

150

100

50

0

150

120

90

60

30

00 10 20 30 40 50 60 70 80

TAXI SPEED - MPH

BEAD

˚C

DISTANCE = 40,000 FTDEFLECTION = 32%

TREAD SHOULDER

TREAD CENTERLINE

0 10 20 30 40 50 60 70TAXI SPEED - KNOTS

TEMPERATURE RISE VS PERCENT DEFLECTION

TEM

PER

ATU

RE

RIS

E ˚F

250

200

150

100

50

0

150

120

90

60

30

015 20 25 30 35 40 45 50

PERCENT (%) DEFLECTION

BEAD

TREAD CENTERLINE

˚C

DISTANCE = 25,000 FTSPEED = 30 MPH

AB

TREAD SHOULDER

CONTAINED AIR

40


Even when an aircraft tire is properly inflated and operated at moderate taxi speeds, the heat generation willalways exceed the heat dissipated. (This is indicated by the ever increasing slope of the lines.) The fartherthe taxi distance, the hotter the tires will be at the start of the take-off.

This chart shows the effect of underinflation coupled with the high speed taxiing. A comparison is madebetween a tire run at 32% deflection and one run at 40% deflection. Not only is the slope of the 40%deflection curves much steeper (due to higher rate of heat generation) than the 32% curve, but the 40%deflection tire blew out in the lower sidewall after traveling about 30,000 feet.

TEMPERATURE RISE VS TAXI DISTANCE

TEM

PER

ATU

RE

RIS

E ˚F

250

200

150

100

50

0

150

120

90

60

30

00 10 20 30 40 50

TAXI DISTANCE - THOUSAND FEET

˚C

SPEED = 60 MPHDEFLECTION = 40%

0 5 10 15TAXI DISTANCE - KILOMETERS

TEMPERATURE RISE VS TAXI DISTANCE

TEM

PER

ATU

RE

RIS

E ˚F

250

200

150

100

50

0

140

120

100

80

60

40

20

-00 10 20 30 40 50

TAXI DISTANCE - THOUSAND FEET

˚C

SPEED = 30 MPHDEFLECTION = 32% BEAD

BEAD

TIRE FAILEDBEAD BLOWOUT

TREAD SHOULDER

TREAD SHOULDER

TREAD CENTERLINE

0 5 10 15TAXI DISTANCE - KILOMETERS

A

A

B

B



41


The carcass or body of the tire is usually made up of rubber-coated layers of nylon fabric which extendfrom bead to bead. This fabric, which is anchored to the bead bundles, is a structural member of thetire to give it shape and strength.

As good as nylon is, it has limitations. There is a reduction in strength when exposed to hightemperatures. Nylon melts at temperatures slightly above 400°F (200°C).

The physical properties of rubber compounds are also susceptible to degradation by high temperatures. Both strength and adhesion are lost when the rubber reverts to the uncured state. The temperatures shown in the above chart are related to time. Brief exposure to these temperaturesare not as damaging to the tire as are prolonged exposures.

Effect of Temperature on Rubber Compounds

EFFECTS °F °C

APPEARANCE OF BLUE COLOR 210 - 230 100 - 110

RUBBER REVERTS 280 - 320 140 - 160

RUBBER BECOMES HARD & DRY 355 - 390 180 - 200

A

On the previous charts it must be remembered that only temperature rise was indicated. Heat is cumulative. This chart shows the time required to cool the bead area of a test tire with two fans blowing on it. This would equal approximately a 30 mph breeze. The curve indicates that the temperature in a hot tire drops 100°F in the first hour and somewhat less in subsequent hours. Thecooling time of a tire mounted on an aircraft would be slightly longer due to the effect of brake temperature.

B

TENSILE VS TEMPERATURE

PER

CEN

T (%

) TE

NSI

LE

100

80

60

40

20

0

TEMPERATURE ˚C

TIME FOR TIRE TEMPERATURE TO DISSIPATE

TEM

PER

ATU

RE

˚F

300

280

260

240

220

200

180

160

140

120

100

140

120

100

80

60

40

TIME (MINUTES)

A B30 80 130 180 230 280 330 380 430 480TEMPERATURE ˚F

0 40 80 120 160 200 240

0 20 40 60 80 100 120 140 160

˚C

42


High internal temperatures deteriorate both compound and fabric, resulting in the following problems:

Tread & Casing Separations - Herewe see separation in both shoulders.The wear pattern indicates this tirewas run underinflated.

Bead Face Damage - Up to now, only heat generated internally has beendiscussed. This is an example of damage due to external heat fromthe brakes.

EXCESSIVESHOULDER

WEAR

SEPARATION

Effects of7 Operating Conditions


43

TENSILE, COMPRESSION AND SHEAR FORCESA discussion of aircraft tires would not be complete without showing the effect of LOAD and SPEED on theTENSILE, COMPRESSION and SHEAR FORCES within a tire.

Tensile, compression and shear stresses can best be visualized by comparing an unloaded tire section to aloaded one as shown in the above photos. The following points can be made:

1. An aircraft tire is designed so that in the unloaded condition the internal tensile forces acting on eachlayer of fabric are uniform.

2. Due to the high deflection of the tire section under the load, the tensile forces on the outer plies will behigher than those on the inner plies.

3. Due to the force gradient from outer to inner plies, shear forces are developed between the various layersof fabric.

4. Underinflating or overloading a tire will increase these shear forces, thus rapidly decreasing the life of anaircraft tire.

UNLOADED CROSS SECTION LOADED CROSS SECTION

44

TENSILE, COMPRESSION AND SHEAR FORCES (CONT’D)

TIR

E PE

RFO

RM

AN

CE

PER

CEN

T (%

)100

90

80

70

60

50

40

30

20

10

00 1 2 3 4 5 6 7 8 9 10

PERCENT (%) UNDERINFLATION

TEST DESCRIPTION: 35,000 FT. TAXI CYCLES AT 40 MPHAT RATED LOAD

40x14

750x230-15

36X10.00-18

To demonstrate how rapid carcass fatigue can occur due to underinflation, the chart above shows the average of three different tire sizes run at the following conditions:

1. One tire of each size was run on successive taxi cycles consisting of 35,000 ft. each at 40 mph. This wasrepeated until tire failure occurred. Since this tire was properly inflated, the test result was recorded as100% durability performance.

2. A second tire of each group was run to the same test, but was 5% underinflated.

3. A third tire of each group was also run to the same test, but at 10% underinflation.

Obviously, one would expect the tire durability to decrease with underinflation. What’s impressive, however, is the magnitude of reduction.

To further study the effect of underinflation on tire failure, additional tests were run on the dynamometer.Several tires, at various degrees of underinflation, were run to failure. Some tires were run to take-off cyclesand others to 10,000 ft. taxi cycles. As would be expected, the cycles to failure decrease as the percent ofunderinflation increases.

CARCASS FATIGUE DUE TO UNDERINFLATION



45


To determine if overloading has the same detrimental affect on tire life as underinflation, the same testswere run on several tires with increasing overloads. As expected, the more a tire is overloaded the quicker it fails.

A couple of interesting findings in this study were that all the taxi cycle failures were still lower sidewallblowouts, and only thrown treads occurred during the take-off cycles. This test shows that taxi cycles aremore sensitive to tire overloading.

CYCLES TO FAILURE VERSUS UNDERINFLATION

NO

FA

ILU

RE

NO

FA

ILU

RE

PERCENT (%) UNDERINFLATION PERCENT (%) UNDERINFLATION

TAXI CYCLES(10,000 FT.)

TAKE-OFF CYCLES

33

16

6.48

10.7

7

3 2 1.5 1.2

A couple of interesting findings in this study were that all the taxi cycle failures were blowouts in the lowersidewall, while the take-off cycle failures were thrown treads. From the shape of the curves we see that take-off cycles were more sensitive to underinflation than were taxi cycles.

10 20 30 40 500 10 20 30 40 50

CYCLES TO FAILURE VERSUS OVERLOAD

NO

FA

ILU

RE

NO

FA

ILU

RE

PERCENT (%) LOAD PERCENT (%) LOAD

TAXI CYCLES(10,000 FT.)

TAKE-OFF CYCLES

10

4.51.72.23.0

25

12

86

4.6

110 120 130 140 150100 0 110 120 130 140 150

46


Tensile, compression, and shear forces in aircraft tires are extremely high. When the tires are not properlymaintained, these forces go even higher until the compound and/or fabric start rapid deterioration. Whenthis happens the following problems can occur:

SHOULDER SEPARATION

Shoulder separation is most likely to occur between outer plies where the shear forces are highest.

LOWER SIDEWALL COMPRESSION BREAK

This is the start of the type of failure caused by underinflation or overloading. The above photo showscarcass cords above the bead area that are starting to fail due to flex fatigue.



47


These photos show how underinflation or overloading can cause lower sidewall compression flex breaks.

Massive Separation - Duringthe creation of a sidewall orliner crack, the carcass plies onthe inside become severely deteriorated, along with massiveseparations. This results in possible sidewall blowout.

Liner Crack - The first signs of acompression flex break can alsoappear on the inside liner. Thiscondition will also be apparentby tire pressure loss. This pressureloss then magnifies the problem,resulting in sidewall blowout.

Sidewall Crack - The first signsof compression flex break in thelower sidewall can appear on theoutside sidewall or the insideliner. This photo shows a crackdeveloping in lower sidewall.

These three photographs show the stages of progression. Never mistake these conditions for simply a sidewall or liner crack, as a blowout is imminent.

48

TIRE INFLATIONHeavy loads and high speeds are here to stay. In fact, they will probably get worse in the future. If they do,centrifugal force, heat generation, tensile, compression and shear forces will also increase.

This section has shown that aircraft tires will function properly only when they have the correct inflationpressure. It has also shown that there is a relatively small amount of tolerance in the amount of deflectionin which the tire can operate effectively.

Many times we think we can look at the tire deflection and determine if it is under-inflated as we often dowith our passenger car tires. This judgment is even more difficult with the aircraft sitting unloaded and lowfuel, a condition typical when tire pressures are taken.

QUESTION: Can you tell which tire in this nose gear is underinflated?

ANSWER: No. You cannot tell by looking. The “mate” tire will share the load and the two tires will lookequal. Therefore, you should always use a calibrated inflation gauge to check tire pressure.

On a four-wheel or six-wheel gear, visual inspection of a low pressure tire is even worse, as there are moretires picking up the load from the underinflated tire.

IMPORTANT - INFLATION PRACTICES

(See Section 2, Proper Inflation Procedures)

1. CHECK DAILY WHEN TIRES ARE COOL2. INFLATE TO WORST CONDITIONS 3. USE DRY NITROGEN GAS (SAFELY)4. INCREASE PRESSURE 4% FOR TIRES UNDER LOAD5. ALLOW 12-HOUR STRETCH AFTER MOUNTING6. NEVER REDUCE THE PRESSURE OF A HOT TIRE

REMEMBER – 1% PRESSURE CHANGE FOR 5°F (3° C) 7. EQUAL PRESSURE FOR DUALS8. CALIBRATE INFLATION GAUGE REGULARLY

NOTE: Following the suggested maintenance procedures and operating techniques in this manual cangreatly extend tire life.


49

LIMITED WARRANTY FOR GOODYEAR NEW AIRCRAFT

TIRES, TUBES AND RETREADS

Goodyear warrants that, when operated and maintained in accordance with approvedinstructions, every new tire or tube bearing Goodyear’s name and complete serial number,or retread bearing Goodyear’s or Air Treads’ name and serial number, is warranted to befree from defects in workmanship and material. The sole and exclusive remedy for thecustomer for a tire, tube, or retread returned to us freight prepaid and determined by us tobe defective, or which there is a pro-rata charge for service, is the repair or replacement ofsuch tire, tube, or retread, or other suitable allowance.

EXCEPT AS STATED ABOVE, THERE ARE NO WARRANTIES, EXPRESS ORIMPLIED, AND SUCH TIRES, TUBES, AND RETREADS ARE NOT WARRANTED FORMERCHANTABILITY OR FITNESS FOR ANY PARTICULAR PURPOSE, APPLICATION,PERFORMANCE OR USE AND THERE IS NO OBLIGATION OF THE SELLER AS TOTHE CONFORMITY OF THE GOODS. SELLER’S LIABILITY WHETHER UNDER ANYWARRANTY OR IN CONTRACT, NEGLIGENCE, TORT, STRICT LIABILITY OROTHERWISE SHALL NOT EXCEED THE NET PURCHASE PRICE AFTER ALLDISCOUNTS INCLUDING CASH DISCOUNTS, AND IN NO EVENT SHALL SELLERBE LIABLE FOR SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES. THEFOREGOING IS EXCLUSIVE AND IN SUBSTITUTION FOR, AND CUSTOMER HEREBYWAIVES, ALL OTHER WARRANTIES, GUARANTIES, RIGHTS, REMEDIES ANDOBLIGATIONS. No representative has authority to modify or make any representation,promise or agreement, except as stated herein.

Do not return any item without prior approval. Contact your Goodyear Aviation TireRepresentative for instructions.

50

NOTES

51

TIRE PERFORMANCE ENVELOPE

OFF-ROADTIRE LOAD CAPACITY

(X1000 LB)

TRUCK AND FARMTIRE LOAD CAPACITY

(X1000 LB)

RACE, PASSENGER

AND LIGHT TRUCK

TIRE LOAD CAPACITY(X1000 LB)

TIRE OPERATIONAL SPEED (MPH)

AIRCRAFTTIRE LOAD CAPACITY(X1000 LB)

AIRCRAFT

LIGHT TRUCK

PASSENGERRACE

TRUCK

OFF-ROAD

FARM

Aviation TiresThe Goodyear Tire & Rubber Company

1144 East Market StreetAkron, Ohio 44316-0001, U.S.A.

PH: 330-796-6306Fax: 330-796-6535

©2002, 2003, 2004. The Goodyear Tire & Rubber Company. All rights reserved.

www.goodyearaviation.com

(012096) 10/04700-862-931-538

Aircraft Tire Manual

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